Cook was convicted of murdering two co-workers, a man and a 16-year-old boy, in separate killings within hours of each other in Lake Havasu City.

The appeals court rejected Cook’s claim that he had ineffective legal representation. The ruling notes that Cook decided to represent himself during the trial and earlier withheld information about his troubled upbringing from his pretrial lawyer.

Another man who participated in the killings was released from prison after serving 20 years for second-degree murder.